Pulmonary Hypertension Guidelines For Echo: And How To Measure RVSP
You probably don’t need to be told that echocardiography plays a major role in the noninvasive assessment of pulmonary hypertension. Echo is used to not only screen for the disease, but to determine right and left heart structure and function as well as monitor the progress of patients undergoing treatment for pulmonary hypertension.
What Is Pulmonary Hypertension
According to the Mayo Clinic, pulmonary hypertension (PHTN) is a type of high blood pressure that affects the arteries in your lungs as well as the right sided chambers of your heart.
The Journal of the American Society of Echocardiography states that pulmonary hypertension results in right ventricular pressure overload, which ultimately leads to right heart failure and death.
The Journal continues to state that, “pulmonary hypertension has an estimated prevalence of 30 to 50 cases per million individuals, affects women more frequently than men, and can be idiopathic, heritable, drug or toxin induced, or associated with other medical conditions, such as congenital heart disease (CHD), connective tissue disease, human immunodeficiency virus infection, portal hypertension, schistosomiasis, and chronic hemolytic anemia.”
Pulmonary Hypertension In Echocardiography
So what does echocardiography, or cardiac ultrasound, have to do with pulmonary hypertension? Well, to be honest, echo plays a critical role in screening for pulmonary hypertension.
In the same article from the Journal Of The American Society of Echocardiography, it mentions that, “Given the nonspecific symptoms and subtle physical signs, particularly in the early stages, [of PHTN] a high clinical index of suspicion is necessary to detect the disease before irreversible pathophysiologic changes occur. In this regard, transthoracic echocardiography, by providing direct and/or indirect signs of elevated pulmonary artery pressure (PAP), is an excellent noninvasive screening test for patients with symptoms or risk factors for PAH, such as connective tissue disease, anorexigen use, pulmonary embolism, heart failure, and heart murmurs. It may also provide key information on both the etiology and the prognosis of PH.”
In short, what their saying is that echo is a great way to not only screen for PHTN, but that echo also provides information on the cause and the prognosis.
So as a cardiac sonographer, if you haven’t noticed yet, we tend to get a lot of patients who have already been diagnosed with pulmonary hypertension, or who are suspected of having pulmonary hypertension.
But what is it specifically we should be looking for with echocardiography in these pulmonary hypertension cases?
Well that’s exactly what we’re going to go over in this article…
So let’s dive right in.
Pulmonary Hypertension Echo Guidelines
Current pulmonary hypertension echo guidelines recommend that echocardiography be used in the initial evaluation of patients who are suspected to have PHTN to assess:
- Pulmonary artery pressure (PAP)
- Right atrial enlargement (RAE)
- Right ventricular size and function
- Pericardial effusions
- Left ventricular systolic and/or diastolic dysfunction
- Left atrial and left ventricular size and function
- and valvular disease
In this post, we are going to focus on screening for pulmonary hypertension with echo by measuring the pulmonary artery systolic pressure. This measurement alone can tell us a lot.
So how do you assess for pulmonary hypertension using echocardiography? I’ll show you how.
Let’s dive right in!
How To Assess For Pulmonary Hypertension With Echocardiography
Like I mentioned earlier, echo plays a critical role in not only helping diagnose pulmonary hypertension, but also in helping learn what might be causing the increased pulmonary pressures.
For example, a patient who has significant mitral stenosis can also present with pulmonary hypertension. As a matter of fact, PHTN is something you should always interrogate in these cases.
Ultimately, we want to know what the Pulmonary Artery Systolic Pressure is (PASP). This is the measurement that we’re most interested in. But how do we measure pulmonary artery systolic pressure (PASP) with echocardiography?
Here’s what we’re going to do:
PASP = RVSP + RAP
And it all starts with tricuspid regurgitation.
Tricuspid Regurgitation and Pulmonary Hypertension
Functional tricuspid regurgitation is a common side effect of pulmonary hypertension. But not everyone with tricuspid regurgitation (TR) has pulmonary hypertension.
But the good news is, we can use the existing tricuspid regurgitation to help us determine the patient’s pulmonary artery pressure, (PAP) which is what we’re trying to ultimately get to in order to determine whether or not they have pulmonary hypertension.
Right Ventricular Systolic Pressure (RVSP) And Echo
The way we do this is by using echo to measure the right ventricular systolic pressure, or RVSP.
Right Ventricular Systolic Pressure (RVSP) in echo is obtained by simply measuring the pressure gradient of the tricuspid regurgitant jet.
How To Measure RVSP in Echo
To measure the RVSP in echo, all you need to do is line up your cursor parallel with the tricuspid regurgitant jet and turn on continuous wave Doppler. This will give you the peak velocity of the TR jet.
Now to find out the pressure gradient, all you need to do is plug it into the formula 4V2. Here’s what it will look like.
Pressure Gradient Formula: 4 x V2
Say that the peak TR velocity was 2.5 m/s. We would start by multiplying that by itself (V2).
V2 = 2.5 x 2.5
V2 = 6.25
Next we multiply V2 by 4.
4 x V2 = 25
And since we’re looking for a pressure gradient as the answer, we assign it mmHg.
Answer: 25 mmHg.
Let’s try another example.
With your continuous wave Doppler, you measure a peak velocity of the tricuspid regurgitant jet of 3.7 m/s.
You remember that the formula for pressure gradients is 4 x V2. So you plug in the info.
3.7 x 3.7 = 13.69
4 x 13.69 = 54.76 mmHg
Right Atrial Pressure (RAP) and Echo
The next thing we need to do to obtain the PASP is figure out what the right atrial pressure is (RAP), and add it to the RVSP.
So how do we figure out what the RAP is?
We know that the inferior vena cava is attached to the right atrium. So if we can estimate what the pressure is in that section of the IVC, then we can assume that the pressure in the right atrium is the same or similar. (This is true because there is no valve between the right atrium and the IVC).
For a complete guide on how to accurately estimate RAP and to learn more about the Inverior Vena Cava and how it’s used in echo, be sure to read my post, IVC Assessment With Echo: What Does IVC Collapse Even Mean?
In short, in order to estimate the RAP, you need to measure the diameter of the IVC and then look to see if the IVC collapses more than 50% of its diameter, or less than 50% of its diameter.
Below is a chart explaining what the estimated right atrial pressure is based on your findings.
IVC Collapsibility Index For Mean Right Atrial Pressure
Normal Diameter Collapses 3 mmHg
Normal Diameter Does Not Collapse 8 mmHg
Dilated Collapses 8 mmHg
Dilated Does Not Collapse 15 mmHg
So if a patient has an IVC that measures 1.9 cm and it collapses more than 50%, they would have an estimated mean RAP of 3 mmHg.
Puting It All Together For The Pulmonary Artery Systolic Pressure (PASP)
Now that we’ve figured out what the right ventricular systolic pressure (RVSP) is and the right atrial pressure (RAP), we can add them together to get the pulmonary artery systolic pressure (PAP).
If you recall, we said that:
PAP = RVSP + RAP
So if we plug in what we know from the above examples…
54.76 mmHg + 3 mmHg = PAP of 57 mmHg
Normal RVSP and Normal Pulmonary Artery Pressure
Now that you’re able to determine what a patients pulmonary artery pressure is by measuring the RVSP, what does it actually mean.
Average cardiac sonographers will simply record these measurements and move on without fully understanding or comprehending what it is that they’re measuring.
But a good cardiac sonographer will have a good understanding of what normal is, that way they can interrogate further if necessary.
Since we all want to be better sonographers, lets take a look at what the normal values are for RVSP and PAP.
There are times when you may only need to know what the RVSP is. And you can determine whether a patient has PHTN by measuring just the RVSP. Often times, you’ll be specifically asked to measure just the RVSP for a physician.
So what is a normal rvsp?
To accurately determine this, we would really need divide our patients up into groups based on age, as RVSP begins to signficantly increase after the age of 50 in both men and women. According to The Canadian Journal Of Cardiology, “…the echocardiographic estimate of right ventricular systolic pressure (RVSP) increases progressively and normally with age.”
With that said, however, there are some parameters we can use on a general basis to keep things simpler in our echo lab. The below values were obtained from the American Society Of Echocardiography.
Normal RVSP = <36 mmHg
Anything over this measurement can be considered as pulmonary hypertension.
Or, if you don’t want to take the time to calculate the RVSP, you can simply translate that into a normal TR pressure gradient.
Normal peak TR pressure gradient = 2.8 – 2.9 m/s.
Now you’re equipped to get out there and accurately assess for pulmonary hypertension with the use of echocardiography. But just remember, that calculating the RVSP or the PASP is not the end.
Echo guidelines for pulmonary artery hypertension also recommend that you take a close look at right heart chambers size and function.
Echo is a great tool in the evaluation of pulmonary hypertension, and we’re lucky to be a part of that important role as cardiac sonographers. So take your time to make sure you obtain accurate measurements and hunt down that peak TR pressure gradient from multiple windows!